1. Field of the Invention
This invention provides polysiloxane-polyoxyalkylene terpolymers for the manufacture of conventional flexible polyurethane foam. The invention also provides a process for producing conventional flexible polyurethane foam formulations using these terpolymers as foam stabilizers, including flame retardant foams. The invention further provides conventional flexible polyurethane foam produced using the terpolymers of the invention including flame retardant flexible polyurethane foams.
2. Description of Prior Art
Polysiloxane-polyoxyalkylene copolymers were first disclosed in U.S. Pat. No. 2,834,748 (Bailey et al., 1958). These compositions were of the hydrolyzable type. Non-hydrolyzable polysiloxane-polyoxyalkylene copolymers were first disclosed in U.S. Pat. No. 2,846,458 (Haluska, 1958).
The first use of polysiloxane-polyoxyalkylene copolymers for the stabilization of one-shot flexible polyurethane foam appeared in Brit. Pat. No. 892,136 (Hostettler, 1958). The stabilizers so described were of the hydrolyzable variety. The application of non-hydrolyzable copolymers to the stabilization of polyurethane foams soon followed.
U.S. Pat. No. 4,478,957 discloses the use of certain polysiloxane-polyoxyalkylene block copolymers for the production of highly resilient, cold-curing polyurethane foams. These copolymers as defined are limited to lower molecular weight species (less-than-or-equal-to an average of 25 silicon atoms in the siloxane chain) and contain at least two polyoxyalkylene blocks, which are formed from oxyethylene and oxypropylene units, wherein one such block has a weight percent oxyethylene range of from 38 to 100% (45-100 mole %) and the other such block has an oxyethylene weight percent range of from 0 and 57% (0-50 mole %). The molecular weights of the polyoxyalkylene blocks are both between 150 and 1200 and the molar ratio of one block to another falling in the range of 0.25 to 4.00.
These block copolymer compositions showed improved stabilizing properties and formed open-cell high resilient foams at a relatively wide processing latitude. Those skilled in the art recognize that siloxane surfactants for high resilient (HR) urethane foam provide insufficient stabilization for conventional flexible urethane foam since HR surfactants serve primarily as cell control agents in the inherently more stable high resilient foam formulations.
Additionally, U.S. Pat. No. 4,031,044 discloses the use of polysiloxane-polyoxypropylene copolymers for the stabilization of high resilient polyurethane foams which have low shrinkage and are free of voids without sacrifice of other important physical properties. Again, those skilled in the art realize the inapplicability of HR surfactants in conventional flexible urethane systems.